Cybersecurity remains a significant concern in today's interconnected world, as attackers become increasingly sophisticated in their malicious actions. Most malware attacks result in a distributed system, formed by the infected hosts actually used to perform the malicious activity, the support hosts (who might be infected or otherwise under the control of the attacker), and the machine(s) directly used by the attacker to control the malware network. Botnets are one example of such distributed systems. Spyware and advanced persistent threats (APTs) each form similarly distributed systems. For example, spyware is often used to collect sensitive information from infected machines and send it to one or more central servers, which in turn propagate the sensitive information to (human or not) agents that use this information to obtain access to more systems or to financial instruments.
Botnets are particularly dangerous because they can be used to launch large-scale, coordinated attacks such as distributed denial of service, spamming, and click fraud based on commands by an external controller.